In recent years, molecules of oligosaccharides have attracted attention as third chain life molecules following nucleic acids (DNA) and proteins. The human body is a huge cell society comprising about 60 trillion cells, and the surfaces of all the cells are covered with oligosaccharide molecules. For example, ABO blood types are determined according to the difference of oligosaccharides over the surfaces of cells.
Oligosaccharides function in connection with the recognition of cells and interaction of cells and are key substances for the establishment of the cell society. Disturbances in the cell society lead, for example, to cancers, chronic diseases, infectious diseases and aging.
For example, it is known that when cells cancerate, changes occur in the structure of oligosaccharides. It is also known that Vibrio cholerae, influenza virus, etc. ingress into cells and cause infection by recognizing and attaching to a specific oligosaccharide.
Oligosaccharides are much more complex than DNA or proteins in structure because of the diversity of arrangements of monosaccharides, modes or sites of linkages, lengths of chains, modes of branches and overall structures of higher order. Accordingly, biological information derived from the structures thereof is more diversified than is the case with DNA and proteins. Although the importance of research on oligosaccharides has been recognized, the complexity and variety of structures thereof have delayed progress in the research on oligosaccharides unlike the studies on DNA and proteins.
E. Meinjohanns (J. Chem. Soc. Perkin Transl. 1998. pp. 549-560) et al. prepared a 2-branched asparagine-linked oligosaccharide from bovine fetuin (bovine-derived glycoprotein). They utilized a hydrazine decomposition reaction to obtain a 2-branched oligosaccharide for use as the starting material. Since hydrazine has high toxicity, the application of the oligosaccharide derivatives obtained to pharmaceuticals involves problems as to safety because of the possibility of a trace of hydrazine becoming incorporated into the derivative. 3-Branched asparagine-linked oligosaccharides still remain to be prepared.
An object of the present invention is to provide a 3-branched asparagine-linked oligosaccharide derivative wherein the nitrogen of the amino group of asparagine is modified with a lipophilic protective group, biotin group or FITC group and a process for preparing the derivative.
Another object of the invention is to provide a 3-branched asparagine-linked oligosaccharide, a 3-branched oligosaccharide and processes for preparing these compounds.